Chapter 32: Setting up an X-Terminal

Chapter 32

Setting up an X-Terminal

In this chapter:

	Learning about X-terminals
	Setting up a SuSE Linux box as an X-terminal

In chapter 31 we learned that diskless clients are a very good strategy that eases administration for a workstation pool and preserves resources. We've reached the point where we can spare hard drives on the workstations and we can administer all client issues on the server machine a single machine so that updates, changes of the setup, etc. can be done in a central place. No problem you say -- you install them on a central server and everyone can log on to this machine to use the application. Good idea, but it still isn't optimal solution. You have to explain to users which machine holds applications and show them how to use X applications remotely. Wouldn't it be nicer if your users logged onto the application server in the first place? This is exactly what X-terminals are all about. The concept behind X-terminals is to have 'dumb' machines which only run the X-server. Everything else, including login, window manager, etc., run on a server machine. With this method, client maintenance effords are nearly zero. Once it's set up, you can pretty much forget about it. You can turn diskless clients into X-terminals just as regular installed machines, the procedure is exactly the same.

So what do we need to do to achieve this? Not much, since SuSE provides a package which is intended to turn a machine into an X-terminal. The package xdmsc - Xterminal -- Usage SuSE Linux as X terminal contains all the scripts needed to run a SuSE Linux machine Base X Window System - XFree86 3.3. On the server side, you need a running file, xdm. This setup is preconfigured as runlevel three in the SuSE distribution.

For a introduction into runlevels refer to chapter 7.

If we assume the server is running in runlevel three, and the package xdmsc is installed on the client, what else is there to do? The most obvious task is to configure the local X server on the client machine. You won't be able to run an X-terminal without an X server. The SuSE manual takes care of the steps needed to set the X server up, so please refer to this in case you have problems with it. The next step is to set some parameters in /etc/rc.config which are used by the X-Terminal setup:

START_RX
If set to yes the X-terminal is enabled. Use this switch to turn the X-terminal mode on and off.

RX_XDMCP
This determines the type of the X Display Manager Control Protocol (XDMCP) request. XDMCP is used to find hosts willing to manage the X session. Depending on the query type, you may connect to one specific host, or get a list of hosts to choose from. In the latter case you can select the server you want to log on. Three different request types are supported:

	query Query one specific host. The name of the host to query is taken from `RX_HOST` as described below. You can use this option if you want to force the X terminal to log onto a specific machine. In our case this would be the dedicated application server.
	broadcast Sends broadcast query packets to the network. The first responding display manager will be chosen for the session. This setting is useful when you have more than one application server in your network. Whoever answers first gets the session.
	indirect Forwards the query to a specified display manager. `RX_HOST` specifies which display manager will be asked. The result of the request will be presented as a list of hosts willing to take an X session. You then can choose the machine you want to use.

RX_RHOST
Host to send direct and indirect queries to. You have to specify a host here when you set RX_XDMCP to direct or indirect.

Make sure that the host you list here is running xdm. If it's a SuSE Linux machine, you enable xdm by selecting runlevel three as the default runlevel.

RX_DSP
The display number to use on the local display (default is: 0). This setting is optional and you usually don't need to change anything here.

RX_BPP
Number of bits per pixel (color depth). Another optional setting. Usually you set the color depth while you configure the X Window System in /etc/XF86Config. This setting is used as the default for the color depth of the local X server.

Once these settings are done, the last step is to enable xdmsc in /etc/inittab. If you open the file you will find a preconfigured, but disabled line for xdmsc:

#  This is for the package xdmsc, after installing and 
#  and configuration you should remove the comment character 
#  from the following line: 
#7:2:respawn:+/sbin/init.d/rx tty7

The comment pretty much tells you everything there is to do, which is remove the hash sign (#) from the beginning of the line. To activate the X terminal make sure you are in runlevel two (we obviously need the network) and assign init to reread its configuration:

# init 2

Now the X server will be launched and depending on the setting of RX_XDMCP the server will send a query and present a login window or chooser menu. Your X-Terminal is ready to use.

Summary:

We learned that X-terminals are another step towards central administration. Once it's set up, there is almost nothing to maintain

SuSE provides a ready-to-go setup to turn a SuSE Linux box into an X terminal. We saw how to use this setup to get the X-terminal running.